1. Field of the Invention
The present invention relates to an all-terrain vehicle with a speed sensing device. Moreover, the present invention relates to an all-terrain vehicle with a gear transmission.
2. Description of the Related Art
Construction of a four-wheeled all-terrain vehicle and a power train for the four-wheeled all-terrain vehicle will be briefly described. The four-wheeled all-terrain vehicle has a body frame, a pair of front wheels and a pair of rear wheels supported on the body frame, an engine mounted on a part of the body frame between the front and the rear wheels, and steps disposed on the right and the left side of the engine, respectively. A handlebar is supported on an upper part of the body frame, and a straddle-type seat is disposed behind the handlebar. A speed meter (speed indicating device) is held on a middle part of the handlebar. Levers including a brake lever are disposed near the grips of the handlebar.
A crankcase of the engine extends rearward, and a transmission case is joined to the rear end of the crankcase. A gear transmission is built in the transmission case. A variable-speed V-belt drive is disposed on the right side of the crankcase. The output power of the engine is transmitted through the variable-speed V-belt drive to the gear transmission.
A drive shaft is extended in the back-and-forth direction under the transmission case. The drive shaft has a front end connected to a front propeller shaft, and a rear end connected to a rear propeller shaft. The front propeller shaft has a front end part interlocked with a front reduction gear built in a front reduction gear case. The rear propeller shaft has a rear end part interlocked with a rear reduction gear built in a rear reduction gear case.
In the four-wheeled all-terrain vehicle of this type, a conventional speed sensor is placed in a rear axle supporting part of the rear reduction gear case (axle case) and measures the rotation of a rear axle.
Mechanical speed sensors and electric speed sensors are available as a speed sensor of a vehicle. The mechanical speed sensor has a cable or a rod, a gear attached to the cable or the rod and engaged with a gear attached to a rotating member. The cable or the rod, and the gear attached to the same serve as a speed signal transmitting mechanism. The electric speed sensing device has a rotor connected to a rotating member, converts the rotation of the rotor into a corresponding electric pulse signal, and gives the electric pulse signal through a signal line to the speed indicating device.
Referring to FIG. 8 showing a related art speed sensing device disclosed in JP-A 183499/1999 for a vehicle, the speed sensing device 500 is attached to a right side wall of a rear reduction gear case 522 included in an all-terrain vehicle. The speed sensing device 500 has a screw gear 501 supported coaxially with a rear axle 522a for rotation together with the rear axle 522a, a pinion 503 supported for rotation and engaged with the screw gear 501. The rotation of the pinion 503 is measured and a speed signal corresponding to the rotating speed of the pinion 503 is sent through a harness 510 to a speed meter.
When the speed sensing device 500 is attached to the rear reduction gear case 522 as shown in FIG. 8, the speed sensing device 500 is splashed with mud and water while the vehicle is traveling. Since the speed sensing device 500 is distant from the speed meter disposed in a front part of the body frame of the vehicle, and the harness 510 is long, much time and great effort for wiring are required, and the harness 510 must be protected with a cover.
A conventional gear transmission for an all-terrain vehicle includes a chain transmission mechanism as a reversing transmission mechanism interposed between a transmission input shaft and a counter shaft. As shown in FIG. 9, a transmission input shaft 402 connected to a driven shaft 401 included in a variable-speed V-belt drive, a counter shaft (intermediate shaft) 403 and a transmission output shaft 404 are extended in parallel to each other and are supported in a transmission case 400. A forward high-seed gear 405, a forward low-speed gear 406 and a small reverse sprocket 407 are mounted on the transmission input shaft 402. Forward intermediate gears 410 and 411 respectively engaged with the forward gears 405 and 406, an intermediate output gear 413 and a large reverse sprocket 412 are mounted on the counter shaft 403. A chain 415 is extended between the sprockets 407 and 412. An output gear 416 engaged with the intermediate output gear 413, and a bevel gear 422 engaged with a bevel gear 421 mounted on a drive shaft 420 are mounted on the output shaft 404.
A shift dog clutch has a first shift sleeve 425 and a second shift sleeve 426 mounted on the counter shaft 403. The first shift sleeve 425 is interposed between the reverse sprocket 412 and the forward high-speed intermediate gear 410. The second shift sleeve 426 is disposed near the forward low-speed intermediate gear 411.
A shift rod 430 is provided with a first shift arm 431A and a second shift arm 431B respectively engaged with the shift sleeves 425 and 426.
When setting the gear transmission shown in FIG. 9 for a forward high speed or a reverse, the first shift sleeve 425 is shifted. On the other hand, when setting the gear transmission for a forward low speed, the second shift sleeve 426 is shifted. Techniques relating to the present invention are disclosed in JP-A 106162/1987.
Another known gear transmission is not provided with any chain transmission mechanism like that mentioned above, and is provided with a transmission input shaft, a counter shaft and a reverse idle shaft disposed between the transmission input shaft and the counter shaft, and drives an output shaft in the reverse direction by a gear for going backward.
However, those conventional gear transmissions for all-terrain vehicles have the following problems.
(1) Although the gear transmission shown in FIG. 9 including the chain transmission mechanism as a reversing transmission mechanism does not need a reversing idle shaft as an intermediate shaft, the transmission case 400 must be wide because the chain 415 must be a wide one to transmit a large torque, and the chain transmission mechanism requires much assembling work.
(2) In some cases, the chain transmission mechanism needs a tensioner to prevent the generation of rattling noise due to the elongation of the chain 415.
(3) The gear transmission provided with the reverse idle shaft as an intermediate shaft and not provided with any chain transmission needs an additional shaft and hence the transmission case is large and the gear transmission has complicated construction.
Accordingly, it is an object of the present invention to provide an all-terrain vehicle with a speed sensing device capable of being easily protected from mud, water and stones, of being connected to a speed meter by a short harness and of facilitating wiring work.
Another object of the present invention is to provide an all-terrain vehicle with a gear transmission having a transmission case of a comparatively small width and a comparatively short length regardless of being additionally provided with a reverse idle shaft as an intermediate shaft, having simple construction and capable of being assembled by assembling work not requiring much time and great effort.
According to the present invention, an all-terrain vehicle comprises: a variable-speed V-belt drive disposed on one side of a crankcase of an engine; a V-belt drive cover covering the variable-speed V-belt drive; a gear transmission of transmitting a power of the engine in cooperation with the variable-speed V-belt drive; and a speed sensing device including a speed sensor of measuring a rotating speed of a member which transmits the power of the engine to the wheels, the speed sensor being disposed right under the V-belt drive cover.
The speed sensor can be protected from mud and flying stones by the V-belt drive cover and any special protective cover is unnecessary. The speed sensor is disposed nearer to a speed indicator held on a handlebar or the like than the conventional speed sensor attached to the rear reduction gear case, so that the speed sensor can be connected to the speed indicator by a comparatively short harness, therefore, wiring work is facilitated and the harness can be easily protected.
Preferably, the speed sensor measures a rotating speed of a drive shaft which is extended in a back-and-forth direction from an output portion of the gear transmission.
Thus, the speed sensor can be easily attached to a lower part of the V-belt drive cover.
Preferably, the speed sensor is disposed opposite to a driven bevel gear mounted on the drive shaft and engaged with a drive bevel gear of the gear transmission.
Thus, the rotating speed of the driven bevel gear can be directly measured and hence any special member, such as a rotor for speed measurement, is unnecessary and the speed of the vehicle can be measured only by disposing the speed sensor opposite to the driven bevel gear.
Preferably, the speed sensing device further includes: a harness connecting part extending rearward from the speed sensor, and a harness having one end connected to a speed indicator of the all-terrain vehicle, the harness being extended along a component member, which is positioned behind the gear transmission, of a body frame of the all-terrain vehicle to the harness connecting part.
Thus, the harness extending between the speed sensor and the speed indicator can be firmly held on the body frame and can be guided without using any special holding member.
According to the present invention, an all-terrain vehicle comprises: an engine including a crankshaft and a crankcase; a gear transmission of transmitting a power of the engine; and
a transmission case containing the gear transmission. The gear transmission includes: a transmission input shaft having forward gears and a reverse gear, a transmission output shaft and a transmission intermediate shaft all of which are disposed in and supported on the transmission case in parallel to the crankshaft; and a dog clutch mechanism disposed on the transmission input shaft so that one of two forward ratios, a neutral state and a reverse ratio is established by moving a single shift sleeve. The transmission intermediate shaft includes a counter shaft having forward intermediate gears respectively engaged with the forward gears of the transmission input shaft, and a reverse idle shaft having a reverse idle gear engaged with the reverse gear of the transmission input shaft. The transmission input shaft and the transmission output shaft are spaced vertically in the transmission case. The counter shaft is disposed on one side nearer to the crankshaft with respect to a plane including respective center axes of the transmission input shaft and the transmission output shaft. The reverse idle shaft is disposed on other side farther from the crankshaft with respect to the plane.
Thus, while the gear transmission is capable of withstanding a large torque, the transmission case can be formed in a width smaller than that of a transmission case included in a conventional chain type transmission. Since the all-terrain vehicle is of a straddle type, the reduction of the width of the transmission case is effective in increasing spaces for rider""s legs and in improving riding comfort.
Since the transmission input shaft and the transmission output shaft are spaced vertically, and the dog clutch mechanism can be operated by shifting the single shift sleeve to establish one of the two forward ratios, the neutral state and the reverse ratio, a wide space is available for disposing the intermediate shaft. Since the counter shaft is disposed on the side of the crankshaft (front side) and the idle shaft is disposed on the side farther from the crankshaft (rear side), a space under the transmission input shaft and a space in the transmission case between the crankshaft and the transmission input shaft can be efficiently used. Thus, although the gear transmission is provided with one additional shaft as compared with a conventional chain type transmission, the gear transmission is simple in construction and has a comparatively short length.
Preferably, the counter shaft further includes an intermediate output gear. The reverse idle gear includes a first reverse idle gear engaged with the reverse gear of the transmission input shaft, and a second reverse idle gear engaged with the intermediate output gear of the counter shaft. The first and the second reverse idle gears are disposed on one axial end side of the reverse idle shaft.
Thus, a high reduction ratio can be obtained without using a large reverse reduction gear and a large sprocket, and hence the transmission case can be formed in a short length. Since both the two reverse idle gears are disposed on one side with respect to the width of the transmission case, both the two reverse idle gears are disposed near a bearing supporting the reverse idle shaft. Therefore, the operation of the two reverse idle gears are scarcely affected by the bending of the reverse idle shaft, and the accurate engagement of the reverse idle gears with the corresponding gears can be maintained. The ease of incorporating the reverse idle gears into the gear transmission can be improved.
Preferably, the reverse idle shaft is supported on side walls of the transmission case which are opposite to opposite ends of the reverse idle shaft. One end part of the reverse idle shaft, on which the first and the second reverse idle gears are not mounted, is reduced in a diameter smaller than a diameter of other end part of the reverse idle shaft where the first and the second reverse idle gears are mounted.
Thus, the counter shaft and the reverse idle shaft can be disposed at a short center distance by, for example, positioning the outer circumference of the intermediate gear for the forward low ratio, of which diameter is the largest of those of the gears mounted on the countershaft, close to the reduced end part of the reverse idle shaft.